Archived Discussion Main / SpaceIsCold

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&tropeWorking Title: Space Is Cold: From YKTTW

Rogue 7: I swear I heard about this trope in science class, so much so that I accepted it instantly. Learn something new every day, huh?

Radioactive Zombie - I swear that whatever side that light from a star is extremely hot and the other side is freezing. Happens with Mercury.

Large Blunt Object: Because Mercury is crap at retaining heat (basically no atmosphere, incredibly dry), so the energy gets radiated straight back into space. Compare deserts on Earth, which get cold at night without the moderating effect of water and without clouds to reflect radiated heat. Also compare Venus, which because of its excellent heat retention (extremely thick, mainly CO2 atmosphere etc) is hot all over, all the time.

Red Shoe: Back in school, we used to joke about the idea of overclocking a computer and cooling it by generating a vacuum around it, based on the claim that it's cold in space.

Radioactive Zombie: @LBO - Yes, also happens with Mars. Anyway, I've seen a chart at a nearby NASA base that allows schoolchildren to do random stuff related to space. There's a chart showing why you do NOT want to be in space without a suit. You get fried and frozen at the same time, apparently. It's been a while since I have seen the chart, though.

Kilyle: Hey, my dad flat-out called this a lie when I mentioned it to him. He brought up how NASA has to design things capable of withstanding very cold temperatures - e.g., the wheels on a... rover or something, wheels made out of piano wire instead of rubber, because the rubber would freeze. Can you give me some better information on this so I can know how to refute this?

• That's easy. Rovers are built to function on planets and their wheels are in a constant contact with the soil — which is much better heat conductor than vacuum. And, if we take Moon for example, the long nights there could see the soil temperatures to drop to -120C — pretty hard on the rubber. That's why Soviet moon rovers had a bare piano wire wheels, while Apollos' moon buggies had their in a rubber sheath: Lunokhods were designed to withstand several lunar nights, while Rovers were intended to be used for a couple of days during lunar morning. Mars is basically the same, though it has the athmosphere, it's very thin and barely insulating, so it often gets almost just as cold as the Moon in some places.

BritBllt: Though it's true that space isn't physically "cold" the way icy water is cold, the heat loss from infrared radiation emission isn't as negligible as the article makes it sound. Humans radiate at about 1000 watts, and on Earth, surrounded by objects around the same temperature, we get 900 watts of infrared radiation back. So at the least, a person would radiate net body heat ten times faster in the vacuum of space than they would on Earth (and that's not even counting convection and conduction, which are the major temperature stabilizers on Earth). I've read and checked some pretty convincing physics math that suggests your body temperature would hit the freezing point around one hour in a vacuum, due to radiative heat loss. While the trope's right about a lot of movies making it seem like you freeze instantly into an ice cube (and because factors like exposure to sunlight would mean the difference between freezing and roasting to death), there's still a kernel of truth in it.

• Khathi: Would you care to elaborate? I've just estimated this time (assuming that human body in question has the same heat capacity as 70 kilos of water) and got not one, but three hours. And, please note, that 1 kWt power was estimated for completely naked human in a deepest darkness of space. If there's even a bit of clothing, radiative power drops several times, and for a fully clothed individual it's closer to 300 Wt, giving about ten hours.
• RS 14: To be clear, are we considering a corpse at 36C, or a human with a functioning metabolism?
• Photonics: If you assume the human body to be water of mass 75 kg at 37 K with no energy input, and counting only the specific heat capacity at constant pressure of ice (0 K - 273.15 K), water (0 C - 37 C) and the latent heat of fusion of ice, the ratio of the total internal energy of the human body to the rate of energy loss due to blackbody radiation is about 41.62 hours. Given that an object radiates less energy when cooled and the human body not being a blackbody the expected cooling time to ~2.7 K should be about a few times this value.

One thing that struck this troper in the main text of the article is that it keeps implying that the Earth's atmosphere provides protection from the Sun's heat. This is actually the opposite of the truth - without a greenhouse effect, the equilibrium average temperature of the Earth would be below freezing. While the atmosphere does provide protection against UV radiation, overall it increases, not decreases, the temperature on the Earth's surface.

Ununnilium:

• Altho this migth be justified with the fluid in the pod,in which the pilot is immersed) frezing, instead of the entire body getting flash-frozen.

Well, not really; it wouldn't freeze any faster than the body, would it?

• How would Mechs fight in space?! And I'm pretty sure all planets have some sort of atmosphere, otherwise they'd be too small to qualify as planets.
  • Mercury would like to make an objection to your insinuation about its planethood.

Conversation In The Main Page.

• Also in Farscape, Luxans are apparently able to survive about 15 minutes in hard vacuum with no protection.
  • They are seen to be wearing eye protection sometimes.

Not this trope either way.

• Averted by way of making a much worse factual error in one of the Star Wars Expanded Universe novels. In one - Vector Prime, maybe - a plot involved making a planet so very cold that the temperature killed the beings in ships around it, or something. This implies that the temperature was far colder than space, and also effectively requires the laws of thermodynamics to sit down and shut up.

This example is so vague as to be useless; plus, I can't see how it applies to this trope.

Also, there are Real Life examples of the systems with effectively negative absolute temperatures. They are called lasers. ;)

Aphid: I seem to remember an aversion in the Animorphs book The Andalite Chronicles while the characters were trying to retrieve the Time Matrix from the outside of their ship, but I'm uncertain and can't check. Anyone know what I'm talking about?

Photonics: In fact, a large fraction of the interstellar medium is hot. Only a few percent of it is below 300 K; but since the general density is so low it does not heat up objects passing through it seriously. An important problem of astrophysics, in fact, is how these molecule and dust grains cool. Reference: http://en.wikipedia.org/wiki/Interstellar_medium

In addition, slightly more technically-inclined people may get confused by the so-called cosmic microwave background radiation, energy which permeates the known universe at a temperature of about 3 kelvin. A common simplification of this concept is to say that the temperature of space is 3 kelvin — which many take to mean that you'll freeze down to 3 kelvin if you go out there.

This is true in the long run; a person (or any other object) left in space for a prolonged period of time would cool down to the temperature of the surrounding space. There are however two caveats to keep in mind. First, this temperature will only be as low as 3 kelvin if there aren't any other radiation sources (like, say, stars) anywhere nearby: anyone exposed to sunlight in space is actually in danger of roasting to death, not freezing. (Again, go outside on a hot day for proof, and keep in mind that you have a lot of atmo protecting you while you do so. In orbit, it'd be worse.) Second, the "prolonged period of time" required for the human body to freeze in a totally dark vacuum is about an hour, not the seconds (and definitely not the instant flash-freezing) usually shown in movies.

Do not underestimate thermal radiation. Actual cooling speed will greatly depend on your color. if you wear white or metallic costume, there will be relatively little thermal radiation but if you are perfectly black it will be quite cold in space. In any case it won't take very long to freeze to death. However if you are in the earth orbit you are more likely to be cooked by sun heat.

1. conduction (through a solid)
2. convection (through a liquid or gas)
3. radiation (through nothing)

but thinking about this, this is how vacuum containers work in keeping the respective item at the desired temperature. Hm....